TG 10l SOUTH AUSTRALIAN WATER CORPORATION

Transcription

1 TG 10l SOUTH AUSTRALIAN WATER CORPORATION TECHNICAL GUIDELINE GENERAL TECHNICAL INFORMATION FOR GEOTECHNICAL DESIGN ~ Part L ~ Soil Testing Issued by: Manager Engineering Issue Date:

2 SA Water 2007 This document is copyright and all rights are reserved by SA Water. No part may be reproduced, copied or transmitted in any form or by any means without the express written permission of SA Water. The information contained in these Guidelines is strictly for the private use of the intended recipient in relation to works or projects of SA Water. These Guidelines have been prepared for SA Water s own internal use and SA Water makes no representation as to the quality, accuracy or suitability of the information for any other purpose. It is the responsibility of the users of these Guidelines to ensure that the application of information is appropriate and that any designs based on these Guidelines are fit for SA Water s purposes and comply with all relevant Australian Standards, Acts and regulations. Users of these Guidelines accept sole responsibility for interpretation and use of the information contained in these Guidelines. SA Water and its officers accept no liability for any loss or damage caused by reliance on these Guidelines whether caused by error, omission, misdirection, misstatement, misinterpretation or negligence of SA Water. Users should independently verify the accuracy, fitness for purpose and application of information contained in these Guidelines. The currency of these Guidelines should be checked prior to use. No Changes Required In the January 2007 Edition The following lists the major changes to the December 2004 edition of TG 10l: 1. Nil 2 of 6

3 Contents SA WATER NO CHANGES REQUIRED IN THE JANUARY 2007 EDITION... 2 TABLES & FIGURES... 3 SECTION 1: SCOPE... 4 SECTION 2: HAND TEST FOR THE ESTIMATION OF THE CONSISTENCY OF CLAYS AND THE DENSITY OF SANDS WITH CORRELATION TO UCS AND SPT... 4 SECTION 3: ALTERNATIVE IN-SITU TESTS FOR SHEAR STRENGTH PARAMETERS.. 5 Tables & Figures Table Description of Hand Test for the Estimation of Consistency of Clay and the Density of Sand with Correlation to UCS and SPT of 6

4 Section 1: Scope Section 2: Hand Test for the Estimation of the Consistency of Clays and the Density of Sands with Correlation to UCS and SPT Table Description of Hand Test for the Estimation of Consistency of Clay and the Density of Sand with Correlation to UCS and SPT. Material Hand Test (2) Unconfined Compressive Strength q u (1) SPT (blows per 300 mm) Very Soft Clay Easily penetrated 40 mm with fist < 25 kpa < 2 Soft Clay Easily penetrated 40 mm with thumb kpa 2 4 CLAYS Firm Clay Stiff Clay Moderate effort needed to penetrate 30 mm with thumb Readily indented with thumb but penetrated only with great effort kpa kpa 8 15 Very Stiff Clay Readily indented by thumbnail kpa Hard Clay Indented with difficulty by thumbnail > 400 kpa > 30 Loose Sand Clean Takes footprint (~25 kpa) more than 10 mm deep n/a < 10 SANDS Medium- Dense Clean Sand Takes footprint (~25 kpa) 3 mm to 10 mm deep n/a Dense Clean Sand or Gravel Takes footprint (~25 kpa) less than 3 mm deep n/a (1) The unconfined compressive strength (q u ) of a clay is equal to: a. The penetrometer reading. b. Twice the undrained shear strength (2C u ). 4 of 6

5 c. The safe bearing capacity for a typical shallow, vertically loaded, strip footing if the allowable settlement is about 25 mm. (FS = 2 on shear failure.) (2) All field identification tests should be done on a freshly exposed handtrimmed area by an engineer / technical officer competent in such work. Care must be taken to ensure that the soil in the test area was not compacted or loosened during the excavation. The moisture condition of the material at the time of testing must be recorded. If a clay soil is dry, and it is likely that it will become wetter during the life any structure proposed for the location, then the test area should be saturated and the water given time to be absorbed before repeating the trimming and the testing. This Technical Note was prepared by Ed Collingham, 20/01/2003 (Ex Principal Engineer Geotechnical) Section 3: Alternative In-Situ Tests for Shear Strength Parameters Any in situ test for estimating the shear strength parameters as an alternative to the triaxial testing of undisturbed samples would need to have the following attributes: 1. Avoid the difficulties of and disturbance due to recovering samples; 2. Be continuous down the profile to give enough data to pick up the variability and allow averages to be estimated; 3. Be robust to cope with the inevitable rock and stone randomly distributed through the fill; 4. Be a good indicator of "consistency" irrespective of soil type it is assumed likely that (for example) medium dense sands and stiff clays will be found together in a dam; 5. (In association with the previous attribute) test a reasonable volume of the in situ material to provide a "mechanical" averaging; and 6. Provide samples for detailed logging. The only test that appears to meet all these criteria is the Standard Penetration Test. The SPT, apart from being simple and cheap: (a) (b) (c) Is in-situ; Is continuous; Is certainly robust; (d) Has a blow count for loose sands (< 10) similar to that for firm clay (4 to 8), and the blow count for medium dense sands (10 to 30) is similar to that for stiff (8 to 15) to very stiff (15 to 30) clays; 5 of 6

6 (e) (f) Does effectively test a reasonable volume of material because the blow count depends not only on the consistency of the material picked up in the tube but also on the soil surrounding and ahead of the tube; Recovers a reasonable sample for detailed visual/tactile logging and hand penetrometer testing. Other possible in situ tests (such as vane shear tests, pressuremeter or cone penetrometer), variously: are meant for softer clays; would be confused by sands; would be confused by the rapid changes or anisotropy in material type; would be stopped or damaged by stone; do not recover a sample for logging; or would be very expensive to perform. This Technical Note was prepared by Ed Collingham, 06/02/2002 (Ex Principal Engineer Geotechnical) 6 of 6